Combining deep learning method with optical coherence tomography for ablation lesion assessment

The immediate effect of radiofrequency catheter ablation (RFA) on the tissue is not directly visualized. Optical coherence tomography (OCT) is an imaging technique that uses light to capture histology-like images with a penetration depth of 1-3 mm in the cardiac tissue. There are two specific features of ablation lesions in the OCT images: the disappearance of birefringence artifacts in the lateral and sudden decrease of signal at the bottom (Figure panel A and D). These features can not only be used to recognize the ablation lesions from the OCT images by eye, but also be used to train a machine learning model for automatic lesion segmentation. In recent years, deep learning methods, e.g. convolutional neural networks, have been used in medical image analysis and greatly increased the accuracy of image segmentation. We hypothesize that using a convolutional neural network, e.g. U-Net, can locate and segment the ablation lesions in the OCT images. To investigate whether a deep learning method such as a convolutional neural network optimized for biomedical image processing, could be used to segment ablation lesions in OCT images automatically. 8 OCT datasets with ablation lesions were used for training the convolutional neural network (U-Net model). After training, the model was validated by two new OCT datasets. Dice coefficients were calculated to evaluate spatial overlap between the predictions and the ground truth segmentations, which were manually segmented by the researchers (its value ranges from 0 to 1, and "1" means perfect segmentation). The U-Net model could predict the central parts of lesions automatically and accurately (Dice coefficients are 0.933 and 0.934), compared with the ground truth segmentations (Figure panel B and E). These predictions could reveal the depths and diameters of the ablation lesions correctly (Figure panel C and F). Our results showed that deep learning could facilitate ablation lesion identification and segmentation in OCT images. Deep learning methods, integrated in an OCT system, might enable automatic and precise ablation lesion visualization, which may help to assess ablation lesions during radiofrequency ablation procedures with great precision

Subdermal solar energy harvesting – A new way to power autonomous electric implants

Subdermal solar harvesting has the potential to obviate the need for the periodic battery replacements as required in patients with cardiac pacemakers. The achievable power output of the subdermal solar module depends on implantation depth, optical skin properties and to an important part on solar cell characteristics. Monte Carlo simulations of light distribution in human skin were used to estimate the power output of subdermal solar cells under midday sunlight exposure in geographical mid-latitudes as a function of implantation depth and solar panel size. For the darkest skin type, the daily energy demand of a modern cardiac pacemaker (0.864 J at a power demand of 10 uW) can be provided by a 2 cm2 solar cell implanted subdermally at a depth of 3 mm when exposed to just 11 min of midday, clear sky irradiance. Our study reveals that solar harvesting with relatively small solar cells if optimized for the spectral subdermal fluence has the potential to power cardiac pacemakers in all skin types within reasonable irradiation exposure times. Solar energy harvesting is very promising to power electronic implants

Design of percutaneous transluminal coronary angioplasty balloon catheters.

BACKGROUND Eight commercially available percutaneous transluminal coronary angioplasty (PTCA), including semi-compliant and non-compliant balloons, have been assessed in detail on their tip, balloon, shaft, RX-Port, and hypotube design. Important performance characteristics such as tip deformation, balloon elongation, and deflation rate have been quantified. METHODS Five catheters of each model were evaluated during various tests. The robustness of the tips was evaluated through compression, measuring any occurrence of damage. The longitudinal growth of the balloons was recorded during inflation up to Rated Burst Pressure (RBP). The forces required to move the catheter forward and retract it into the guide catheter were measured in a simulated use test setup. The deflation behavior was studied by measuring extracted contrast media over time. Furthermore, balloon compliance and catheter dimensions were investigated. RESULTS The outer dimensions of the catheter were found to be smallest at the hypotube (0.59-0.69 mm) and highest at the balloon, respectively, the crossing profile (0.9-1.2 mm). The tip diameter increased after compression by 1.7-22%. Cross-sections of the folded balloons revealed a tri- and two-fold, respectively. The measured balloon elongation ranged from 0.6 to 2.0 mm. After the inflation of the balloon, an increase in friction between the guide wire and the catheter was observed on four catheters. A maximum increase of 0.12 N to 1.07 N was found. Cross-sections of the RX-Port revealed a semicircular-shaped inflation lumen and a circular guide wire lumen. The measured deflation rate ranged from 0.004 to 0.013 µL/s, resulting in an estimated balloon deflation time of 10.2-28.1 s. CONCLUSION This study provides valuable insights into the design characteristics of RX PTCA balloon catheters, which can contribute to facilitating the development of improved catheter designs and enhancing clinical outcomes. Distinctions between SC and NC catheters, such as balloon performance and dimensions, are evident. It is important to note that no single catheter excels in all aspects, as each possesses unique strengths. Therefore, it is essential to consider individual intervention requirements when selecting a catheter. The research also identifies specific catheter weaknesses, such as reduced wall thickness, fringes at the tip, and reduced performance characteristics

39K and 77Se NMR study of the paraelectric-to-incommensurate phase transition of K2SeO4

Topic B, von Kienlin A, Gölzhäuser A, Haeberlin U, Blinc R. 39K and 77Se NMR study of the paraelectric-to-incommensurate phase transition of K2SeO4. Physical Review, B. 1988;38(13):8625-8632.The 39K quadrupole-coupling and chemical-shift tensors have been determined from the angular dependences of the 39K line shifts of the 39K±(1/2 ± 1) / 2 central NMR transitions in the paraelectric (P) and incommensurate (I) phases of K2SeO4. The main effect of the P-I phase transition on these tensors is the appearance of nonzero off-diagonal elements Vab and Vbc which reflects the destruction of mirror planes by frozen-in soft-mode displacements along the b axis. From the angular dependences of the 77Se line shifts the 77Se chemical-shift tensor has been determined in the paraelectric phase of K2SeO4. In contrast to the 39K quadrupole-coupling and chemical-shift tensors it remains unaffected on going through TI and changes only slightly at TC

Dynamical decoupling of a qubit with always-on control fields

We consider dynamical decoupling schemes in which the qubit is continuously manipulated by a control field at all times. Building on the theory of the Uhrig Dynamical Decoupling sequence (UDD) and its connections to Chebyshev polynomials, we derive a method of always-on control by expressing the UDD control field as a Fourier series. We then truncate this series and numerically optimize the series coefficients for decoupling, constructing the CAFE (Chebyshev and Fourier Expansion) sequence. This approach generates a bounded, continuous control field. We simulate the decoupling effectiveness of our sequence vs. a continuous version of UDD for a qubit coupled to fully-quantum and semi-classical dephasing baths and find comparable performance. We derive filter functions for continuous-control decoupling sequences, and we assess how robust such sequences are to noise on control fields. The methods we employ provide a variety of tools to analyze continuous-control dynamical decoupling sequences.Comment: 22 pages, 10 figure

Advanced Technologies for Oral Controlled Release: Cyclodextrins for oral controlled release

Cyclodextrins (CDs) are used in oral pharmaceutical formulations, by means of inclusion complexes formation, with the following advantages for the drugs: (1) solubility, dissolution rate, stability and bioavailability enhancement; (2) to modify the drug release site and/or time profile; and (3) to reduce or prevent gastrointestinal side effects and unpleasant smell or taste, to prevent drug-drug or drug-additive interactions, or even to convert oil and liquid drugs into microcrystalline or amorphous powders. A more recent trend focuses on the use of CDs as nanocarriers, a strategy that aims to design versatile delivery systems that can encapsulate drugs with better physicochemical properties for oral delivery. Thus, the aim of this work was to review the applications of the CDs and their hydrophilic derivatives on the solubility enhancement of poorly water soluble drugs in order to increase their dissolution rate and get immediate release, as well as their ability to control (to prolong or to delay) the release of drugs from solid dosage forms, either as complexes with the hydrophilic (e.g. as osmotic pumps) and/ or hydrophobic CDs. New controlled delivery systems based on nanotechonology carriers (nanoparticles and conjugates) have also been reviewed